The 5.8-magnitude temblor struck Aug. 23, about 12 miles from North Anna. TheU.S. Nuclear Regulatory Commissiondispatched inspectors to the site and found that no radioactive material beyond what’s normal was released during the event.

But they found that 25 of the 27 casks that store spent nuclear fuel moved 1/2 inch to a 4 1/2 inches during the quake, the union report says. They also determined that instruments designed to detect earthquake activity did not work properly, according to the report.

Despite the severity of the earthquake, the union identified several other incidents it deemed more serious breaches of security.